A fanciful illustration of an alien megastructure harnessing the energy of a star.
NASA

In 2015, citizen scientists found weird dimming and brightening from a star called KIC 8462852, or Tabby's Star.

Astronomers at the time said they couldn't rule out alien activity as an explanation.

However, an exhaustive new study by more than 200 astronomers mostly debunks this wild possibility.

The mystery of Tabby's Star remains unsolved.

The mystery of a star located about 1,300 light-years from Earth is finally coming into clearer focus — and it's not aliens.

A strange brightening-and-dimming behavior of Tabby's Star, or KIC 8462852, was first studied by professional astronomers in 2015. The researchers hadn't seen anything like it, and said they could not rule out alien activity as one remote yet possible cause, such as a Dyson sphere or "alien megastructure" built around the star to harvest its energy.

"It's been called the most mysterious star in the galaxy," Jason Wright, an astronomer at Penn State University who's studied Tabby's Star, told Business Insider. "We call it the 'WTF' star" (an abbreviation, he added, that stands for "where's the flux?").

Following a crowdfunded campaign to observe Tabby's Star in the most detail ever recorded, however, more than 200 scientists are now debunking the wildest explanation.

"There's no reason to think aliens have anything to do with Tabby's Star, given these data," Wright said.

Wright coauthored a new study about the star, published Wednesday in Astrophysical Journal Letters, that was led by Tabetha Boyajian, an astronomer at Louisiana State University who also spearheaded the new observations.

"Dust is most likely the reason why the star's light appears to dim and brighten," Boyajian in a press release.

The mystery of Tabby's Star

An illustration of NASA's Kepler space telescope.
NASA
The weird dimming of Tabby's Star was first detected by NASA's Kepler space telescope, which stared down about 145,000 stars and measured their brightness from 2009 through 2013.

But the actual discovery was made in the 2010s by the "Planet Hunters," a group of volunteer citizen scientists who combed through Kepler data looking for tiny, characteristic dips in brightness caused by orbiting worlds. The project helped discover thousands of planets beyond the solar system, including a few dozen Earth-size and potentially habitable worlds.

During this effort, multiple volunteers described KIC 8462852 as an "interesting" and even "bizarre" star. Over periods ranging from five to 80 days, its brightness would dip a whopping 22% — an amount far greater than any planet in the solar system could cause by passing in front of the sun (and Tabby's Star is 50% larger and 1,000 degrees hotter than our sun).

By September 2015, Boyajian and other professional astronomers took a closer look at the data and confirmed the never-before-seen oddity.

A crowdfunded astronomical discovery

An illustration of dust orbiting KIC 8462852, also known as Boyajian's Star or Tabby's Star.
NASA/JPL-Caltech

Lacking quick access to a government observatory or a large source of funding for private observations, the research team turned to amateur astronomers and crowdfunding for help.

"If we can catch it in the act of getting dimmer, then we can point our telescopes at it, and we can study the material that's blocking the starlight," Wright said in a video for the group's 2016 Kickstarter campaign.

The effort ultimately raised over $107,000, and Boyajian, Wright and others purchased time on the Las Cumbres Observatory Global Telescope Network, which uses observatories contracted all over the world to continuously monitor an object of interest in space.

Observations for their "Where's the flux?" project, conducted from March through December 2017, measured Tabby's Star in a variety of wavelengths or "flavors" of light. The data show that whatever anomaly is obscuring Tabby's starlight doesn't block it completely — much more red light gets through than blue light, for instance.

"Whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure," Boyajian said.

An illustration of a black hole from the movie "Interstellar."
Paramount Pictures

The observations also suggest that the star, which is nicknamed after Boyajian, is not oblong-shaped. And it's unlikely that a planetary collision is causing the dimming, since a spike in temperature that such an event would cause hasn't been seen.

Wright likes the idea that a black hole surrounded by a bunch of dust is to blame, yet said it's a "dark horse idea." Not much else is yet known, he added, since the research team has analyzed only about 10% of its mountain of new data.

"It's overwhelming," Wright said. "It sort of feels like a Christmas where everyone gets you books, and at the end of the day you have this enormous stack — but you have no idea where to start or how long it's going to take to get through it all."

However long it takes, Wright says it's important to solve the mystery of Tabby's Star.

"Kepler only looked at one part of the sky, and this was one of 100,000 stars. But there are hundreds of billions of stars in the galaxy," he said. "So there could be billions of these out there, too."